There is ever-increasing consumer demand for services, such as data, voice, and video, to be delivered over broadband communications systems. Cable modem technology is one method of providing such broadband services to subscribers. In the 1980s, cable television providers built out significant physical plants that resulted in millions of individual customer premises being connected (or “wired”) directly with a cable headend system from which cable television programming was broadcast. Over time, it was realized that the connectivity between the headend system and customers could be leveraged to supply additional services such as on-demand television programming, as well as more sophisticated voice and data services.
The Data Over Cable Service Interface Specifications (“DOCSIS”) standard specifies the transfer of Internet Protocol (IP) traffic, between the cable headend system and customer locations, over an all-coaxial or a hybrid-fiber/coax (HFC) cable network. In many cable systems, DOCSIS enables the more sophisticated voice and data services to be delivered to customer premises. The communication infrastructure in a DOCSIS implementation may include a Cable Modem Termination System (CMTS) at the cable headend, and a Cable Modem (CM) at each customer location. With this basic architecture, DOCSIS can deliver IP traffic to a cable modem, enabling a given customer to enjoy any service that such an IP connection can provide including, but not limited to, Internet browsing service, telephony service, as well as television service, perhaps in the form of IP television (IPTV). In the context of DOCSIS, the spectrum used by cable system service providers has generally included, in the United States, a 50-870 MHz forward or downstream band and a 5-42 MHz reverse or upstream band. The downstream band is used by the CMTS to deliver the services requested by customers (television, etc.) toward respective cable modems, whereas the upstream band is used by the respective cable modems to communicate with the CMTS, thus enabling, e.g., a computer at the customer premises to communicate with, e.g., third party web servers with which the CMTS is able to communicate. In light of the large number of fielded CMs, a CMTS is configured with a scheduler that communicates with all of the CMs and notifies the CMs as to when they can respectively communicate upstream in an allocated predefined time slot, in, e.g., a time division multiple access (TDMA) manner (although orthogonal frequency division multiple access (OFDMA) can also be used by the CMs).